Air-bone gap in ears with a well-repaired tympanic membrane after Type III and Type IV tympanoplasty.

Objective: To investigate the air-bone conduction hearing gap (A-B gap) after Type III and Type IV stapes columella tympanoplasty in ears with mobile stapes and a well repaired tympanic membrane (TM).
Methods: Those patients who underwent tympanoplasty in our hospital between 2003 and 2009 and satisfied the following criteria were eligible: (1) good stapes mobility, confirmed intraoperatively; (2) postoperative TM and/or computed tomography (CT) findings that showed a well-aerated tympanic cavity without TM perforation, otorrhea, or middle ear effusion; and (3) measurable air and bone conduction hearing thresholds 1 year postoperatively at all test frequencies (250 Hz, 500 Hz, 1 kHz, 2 kHz, and 4 kHz).
Results: Hearing results were better after Type III tympanoplasty than after Type IV tympanoplasty. After Type III (n=70) and Type IV (n=24) tympanoplasty, the respective mean A-B gaps were 16.4 ± 7.2 dB and 20.1 ± 5.6 dB, respectively. The mean A-B gap was significantly smaller after Type III tympanoplasty than after Type IV tympanoplasty (p<0.05). Regardless of the type of tympanoplasty, the postoperative A-B gap was greatest at 4 kHz.
Conclusion: The mean A-B gap was smaller after Type III tympanoplasty than after Type IV tympanoplasty. The magnitude of the A-B gap was greatest at 4 kHz in both procedures.
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